Most customers don't know or care. They walk into the Apple store and ask for the "newest MBP." Never will a customer ask the generation of a processor. Apple knows this. If they announced new rMBPs now, months in advance, the majority of customers will stall, and Apple will lose rMBP sales until that time.
They cant risk losing sales, by announcing new rMBPs to please a minority like us.
What most people fail to realize is that the "Pro" line is also the consumer line (especially the 13"). The only product they've ever gave a heads up on was the Mac Pro, and that was more show boating then giving a **** about their customers. Cause here we are over two years later and still no update on that line either. Apple flat out thinks their brand name is enough to sell anything. Sadly, with many consumers, that's true.